1. Field of the Invention
The invention relates to the field of semiconductor substrate processing equipment. More particularly, the invention relates to an apparatus and method for supporting a substrate during processing.
2. Background of the Related Art
In the fabrication of integrated circuits, equipment has been developed to automate substrate processing by performing several sequences of processing steps without removing the substrate from a vacuum environment, thereby reducing transfer times and contamination of substrates. Such a system has been disclosed, for example, by Maydan et al., U.S. Pat. No. 4,951,601, in which a plurality of processing chambers are connected to a transfer chamber. A robot in a central transfer chamber passes substrates through slit valves into the various connected processing chambers and retrieves them from the chambers after processing is complete.
The processing steps carried out in the vacuum chambers typically require the deposition or etching of multiple metal, dielectric and semiconductor layers on the surface of a substrate. Examples of such processes include chemical vapor deposition (CVD), physical vapor deposition (PVD), and etching processes.
Vacuum chambers are employed in CVD to deposit thin films on semiconductor substrates. Typically, a precursor gas is charged into a vacuum chamber through a gas manifold plate situated above the substrate. In a thermal process the substrate is typically heated to a desired process temperature. The precursor gas charged into the chamber reacts on the heated substrate surface to deposit a thin layer thereon.
Challenges encountered in CVD include material deposition on the edge and back side of the substrate and on the support member. Deposition on the edge and backside of a substrate, for example, can potentially render a substrate incompatible for subsequent processes, such as chemical mechanical polishing (CMP). Material deposited on the edge of the substrate can remain on the edge after CMP and potentially create a particle source or jeopardize the integrity of the device formed by the process. Additionally, material on the edge and backside of a substrate may delaminate and similarly become a particle source. Still further, material deposited on the substrate and support member may cause the substrate to adhere to the support member and may compromise the integrity of the devices formed on the substrate.
In order to mitigate the problems of unwanted deposition on the substrate and the support member, shadow rings and purge gas have come into use. Shadow rings cover the periphery of the substrate during deposition to mask the edge of the substrate to inhibit the deposition gases from contacting the edge and backside of the substrate. However, due to the volatility of some precursor gases, such as WF6, for example, shadow rings alone do not prevent edge and backside deposition on the substrate.
Purge gas directed behind or at the edge of the substrate has been used to prevent edge and backside deposition. The purge gas exerts a positive pressure near a perimeter portion of the substrate that reduces the likelihood that processing gas will reach the edge and backside of the substrate as well as the support member holding the substrate. In systems using a purge gas, a plurality of spaced purge gas orifices formed in the support member deliver the purge gas to the edge of the substrate. However, conventional purge gas systems can result in non-uniform deposition of the material over the surface of the substrate intended to be coated.
As the desire for greater throughput and efficiency in semiconductor device fabrication has increased, integrated circuit manufacturer requirements governing the thickness and uniformity of the deposited film at the substrate edge have become more stringent. Current industry standards demand no film deposition on the beveled edge of the substrate and a film thickness at a point 3 mm from the edge of the substrate that is 90 percent or more of the film thickness at the center of the substrate with a thickness uniformity better than xc2x15 percent, excluding the area within 3mm from the substrate edge (known as the xe2x80x9cexclusionary zonexe2x80x9d).
Therefore, there is a need for a system and method which prevents back side deposition and meets the edge exclusion demands of the industry while not affecting deposition uniformity across the surface of the substrate.
Generally, embodiments of the present invention include apparatus and methods for delivering a gas to the edge of a substrate disposed on a substrate support member. More specifically, the present invention provides a gas delivery apparatus that directs a purge gas to the edge of a substrate at an angle relative to a radial line originating at a center of a deflection member disposed near the substrate.
In one aspect of the invention, an angle of gas flow is controlled by flowing the gas through grooves or other gas deflection structures formed in a gas delivery apparatus. The gas is flowed into an annular opening which provides a fluid passageway by which the gas is flowed into contact with the substrate.
Another aspect of the invention provides a gas delivery apparatus for use in a substrate processing system. The gas delivery apparatus is disposed on a perimeter portion of a support member adapted to support a substrate on a surface thereof. A purge gas passageway is formed in the support member and couples a gas supply to an annular groove. At least a portion of a deflection member is disposed above the annular groove and includes a plurality of grooves or other gas deflection structures adapted to affect a desired flow of purge gas provided from the annular groove.
In another aspect of the invention, a purge gas assembly for directing the flow of a gas a processing system comprises a deflection member having a lower surface defining a deflection surface adapted to direct the flow of the gas at an angle to a radial line originating at a central axis of the deflection member; and an edge ring disposable over at least a portion of an upper surface of the deflection member and comprising an inner annular lip; wherein the deflection member and the edge ring define a portion of a purge gas passageway.
In yet another aspect of the invention, an apparatus for processing a substrate, comprises a support member having a substrate receiving surface and a shoulder portion of the support member disposed outwardly of the substrate receiving surface and having a gas delivery groove formed therein. A deflection member is positioned on the shoulder portion and an edge ring is at least partially disposed over the deflection member. The deflection member defines an interface between a surface of the deflection member and a surface of the shoulder portion. A deflection surface disposed at the interface is formed on at least one of the deflection member and the shoulder portion and is adapted to cause a tangential flow of gas flowing over the deflection surface. In one embodiment, exhaust ports formed in the edge ring are adapted to vent a space at least partially defined by the edge ring.
In still another aspect of the invention, a method for delivering a gas to a substrate supported on an upper surface of a support member in a process chamber is provided. In one embodiment, the method provides comprises providing a gas delivery assembly disposed on a shoulder of the support member, the gas delivery assembly comprises a deflection member and an edge ring having at least a portion disposed over the deflection member; flowing a gas into a gas delivery channel formed in the support member; flowing the gas over a deflection surface disposed on one or more of the deflection member and the shoulder to provide a tangential component to a direction of gas flow; and then flowing at least a portion of the gas into an annular opening formed between the gas delivery assembly and the edge ring.